Truss fabricating machine

ABSTRACT

A truss fabricating machine for forcing truss connector plates into abutting pieces of lumber includes a platform having parallel channels extending the length thereof. Jigging pads rest on the platform and are secured thereto by bolts which thread into retaining elements in the channels. The platform is supported by supporting units, each of which has a pair of leading legs and a pair of trailing legs connected to the leading legs. The legs are movable between upright supporting positions and depressed non-supporting positions. When the leading legs are in their supporting positions, the trailing legs are in the depressed positions, and vice-versa. A gantry press moves along the platform and includes a pair of wheeled carriages, a lower beam extended beneath the platform, an upper beam extended over the platform, and hydraulic press units carried by and movable along the upper beam. The lower beam is secured firmly to one carriage and rests on a bridge bearing on the other carriage so that the wheels of the carriages will follow irregular track surfaces. As the gantry press moves along the platform, it strikes the leading legs of the support units, causing those legs to move to their depressed non-supporting positions and bringing the trailing legs up to their upright supporting positions. The upper beam is a box beam, the interior of which serves as a reservoir for the hydraulic system. Each carriage wheel is powered so the gantry press does not tend to skew on the track.

Elnite States Patent [191 [11] 3,826,188 [451 July 30,1974

Eberle 1 TRUSS FABRICATING MACHINE [76] Inventor: George F. Eberle, 427 Baker Ave.,

Webster Groves, Mo. 63119 [22] Filed: Oct. 24, 1972 [21] Appl. No.: 300,198

[52] U.S. Cl 100/100, 100/193, 100/226,

[56] References Cited UNITED STATES PATENTS 841,150 l/1907 Hoberg et a1. 100/269 X 975,844 11/1910 Egbert 100/226 X 2,250,554 7/194] Schroeder... 105/179 3,241,585 3/1966 Jurcit 144/288 3,334,580 8/1967 Smith 100/226 3,603,244 9/1971 Jurcit et a1 100/100 X Primary Examiner-Billy .l. Wilhite Attorney, Agent, or F irm-Gravely, Lieder & Woodruff [57] ABSTRACT A truss fabricating machine for forcing truss connector plates into abutting pieces of lumber includes a platform having parallel channels extending the length thereof. Jigging pads rest on the platform and are secured thereto by bolts which thread into retaining elements in the channels. The platform is supported by supporting units, each of which has a pair of leading legs and a pair of trailing legs connected to the leading legs. The legs are movable between upright supporting positions and depressed non-supporting positions. When the leading legs are in their supporting positions, the trailing legs are in the depressed positions, and vice-versa. A gantry press moves along the platform and includes a pair of wheeled carriages, a lower beam extended beneath the platform, an upper beam extended over the platform, and hydraulic press units carried by and movable along the upper beam. The lower beam is secured firmly to one carriage and rests on a bridge bearing on the other carriage so that the wheels of the carriages will follow irregular track surfaces. As the gantry press moves along the platform, it strikes the leading legs of the support units, causing those legs to move to their depressed non-supporting positions and bringing the trailing legs up to their upright supporting positions, The upper beam is a box beam, the interior of which serves as a reservoir for the hydraulic system. Each carriage wheel is powered so the gantry press does not tend to skew on the track.

. 15 Claims, 7 Drawing Figures TRUSS FABRICATING MACHINE BACKGROUND OF THE INVENTION This invention relates to an improved truss forming machine, and in particular, to a machine for applying truss connector plates to lumber to form roof trusses and the like.

Truss forming machines have been made in the past and are in present use. These machines either have a high bed, or a restricted bed, or supporting legs which provide obstacles for a moving gantry or are likely to become damaged during their movement out of the path of the gantry.

SUMMARY OF THE INVENTION One of the principal objects of the present invention is to provide a truss forming machine having a bed which is low, flat, and unrestricted. Another object is to provide a table which has novel means, such as grooves, for securing jigging pads on which lumber rests. Another object is to provide a machine wherein the table of the machine is supported on supporting units each having a plurality of legs which are connected together and move as a unit to allow a gantry press to pass both over and under the table throughout substantially the entire length thereof. Another object is to provide a gantry press which has fluid cylinders which can press several truss connector plates into a wooden unit simultaneously. A still further object of the invention is to provide a gantry press whose frame acts as a fluid reservoir. A still further object of this invention is to provide a movable support for a gantry press which comprises a bridge bearing to keep all four wheels on the tracks at all times. These and other objects and advantages will become apparent hereinafter.

The present invention is embodied in a truss forming machine for assembling wooden units with truss connector plates, said machine having a table which is low, flat, and unrestricted and has parallel grooves therein for receiving pads, such pads being used under the place where truss connector plates are applied, said bed being supported on supporting units each having a plurality of legs which pivot as a unit from a supporting position wherein they support the bed to a depressed position where the gantry is free to move by said supporting unit, so that the gantry may move over and pass under the entire length of the bed, said gantry having fluid cylinders which can press the truss connector plates into a unit simultaneously, said gantry having a hollow frame which acts as a fluid reservoir, said frame being mounted on means having a bridge bearing which keeps all four wheels on the tracks for the gantry at all times. The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the specification and wherein like numerals and letters refer to like parts wherever they occur:

FIG. 1 is a perspective view of a truss fabricating machine constructed in accordance with and embodying the present invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2 and showing a supporting unit for the table;

FIG. 4 is an end elevational view of the gantry press forming part of the present invention;

DETAILED DESCRIPTION Referring now to the drawings (FIG. 1), M designates a truss fabricating machine for joining precut pieces of lumber with pronged connector plates to form a roof truss or similar structure. Broadly speaking, the machine M includes a jigging table T, jigging pads J on the table T for positioning the lumber, a gantry press P which moves along the table T and presses the connector plates into the lumber, and supporting units S which support the table T intermediate its ends and depress to permit passage of the gantry press P along the length of the table T. The gantry press P rides on tracks 2 which are bolted to a floor F or other suitable supporting structure.

The table T is disposed between the two tracks 2 and extends substantially the entire length of those tracks 2. It includes a working platform 10 which is supported intermediate its ends on the shiftable supporting units S and at its ends by fixed end supports 12 (FIG. 1) which are bolted to the floor F. The platform 10 has a base 14 (FIG. 7) formed from sheets of /1 inch tongue and groove solid core plywood set edge to edge. Extended over the base 14, longitudinally of the platform 10, are upwardly opening steel channels 16 having inwardly turned flanges 18 at their upper ends. The channels 16 are positioned at equally spaced intervals across the base 14, and those intervals are preferably 12 inches. The channels 16 extend the entire length of the platform 10, and are secured to the base 14 by wood screws 20. Fitted into the spaces between the channels 16 are filler pieces 22 which in turn are covered by top pieces 24. The filler pieces 22 may be A inch plywood, while the top pieces 24 may be Va inch Masonite. The upper surfaces of the top pieces 24 should lie flush with flanges 18 on the channels 16.

The support units S are disposed beneath the table T at equal intervals and provide the platform 10 with subjacent support intermediate the fixed end supports '12. Each support unit S includes (FIGS. 2 and 3) a pair of base plates 30 fastened to the floor F and a pipe sleeve 32 welded to each base plate 30. The sleeves 32 align and serve as bearings for a pivot shaft 34 which extends transversely of the table T close to the floor F. Welded to the pivot shaft 34 adjacent to each of the sleeves 32 are right and left legs 36 and 38, respectively, which are arranged in an open V-shaped configuration with the included angle between the legs 36 and 38 being slightly more than The legs 36 and 38 at each end of the shaft 34 are formed from a single piece of tubing and hence are connected at the apex of the V-shaped configuration. It is at this location that the legs 36 and 38 are welded to the shaft 34. Thus, by virtue of the pivot shaft 34, the right legs 36 at each end of the supportingunit S move in unison and likewise so do the left legs 38. The two right legs 36 are at their extreme outer ends connected by a right cross bar 40 while the two left legs are similarly connected by a left cross bar 42. Both cross bars 40 and 42 are parallel to the pivot shaft 34. The configuration and positioning of the right and left legs 36 and 38 permits them to swing with the shaft 34 between upright and depressed positions. Moreover, when the left legs 38 are in their depressed position the right legs 36 are in the upright position and vice-versa. When either the left legs 36 or right legs are in their depressed position they are disposed generally horizontal and rest upon the floor F. When they are in their upright positions the cross bars 40 or 42 thereon are disposed over center (FIG. 2), that is beyond the pivot shaft 34, so that any downwardly directed force applied to the raised cross bar merely tends to press the depressed legs harder against the floor F. Hence, the support units S do not tend to collapse under the weight of the table platform 10.

The gantry press P includes (FIGS. 2, 4 and a frame 50 which extends transversely with respect to the table T and is supported at its ends on carriages 52 and 54 having wheels 56 which ride on the tracks 2. Each carriage 52 and 54 is further provided with a hydraulic motor 58 of the rotary type and these motors 58 are connected to the carriage wheels 56 through sprocket and chain drives 60 (FIG. 5). The frame 50 is welded firmly to the carriage 52 and is supported on the other carriage 54 by means of a bridge bearing 62 (FIG. 5), the axis of which is parallel to the axes of the wheels 56. Thus, the carriage 54 can pivot a slight amount relative to the frame 50, and this enables the carriage wheels 56 to remain engaged with the tracks 2 even though the tracks 2 may have irregularities. Since the wheels 56 do not leave their tracks 2, all provide the same driving force and their is no tendancy for the gantry press P to skew as it moves along the tracks 2.

The frame 50 includes a lower cross beam 66 which extends between the carriages 52 and 54, and is welded to the carriage 52, but is seated on the bridge bearing 62 at the carriage 54. In addition, the frame 50 has an upper cross beam 68 located above the lower cross beam 66, and a pair of, upright end beams 70 for supporting the upper cross beam 68 above the lower cross beam 66. The lower cross beam 66 is a box beam and has a top plate 72 which is somewhat wider than the remainder of the beam. The plate 72 is located at about the same height of the uppermost cross bars on 40 or 42 when the legs 36 and 38 to which they are attached are in their upright positions. Positioned along each edge of the top plate 72 are rollers 74 (FIGS. 4 and 5) which are somewhat longer than the width of the table platform and each normally has a portion of its circumferential surface above the top surface of the top plate 72 so that normally the platform 10 rests on the rollers 74 and not on the top plate 72. The ends of the rollers 74 are journaled in brackets 76 which pivot about amounts 78 welded to the underside of the top plate 72. The brackets 76 are urged upwardly against the underside of the top plate 72 by springs 80, and when the brackets 76 are so positioned a portion of circumferential surface of each roller 74 is disposed above the upper surface on the top plate 72. However, when sufficient force is applied to the rollers 74, they depress against the force exerted by the springs 80, and when this occurs the underside of the platform 10 will come to rest on the top plate 72 of the lower beam 66. Indeed, as will be apparent in the subsequent discus sion, the top plate 72 serves as an anvil for resisting large forces applied to the platform 10.

The lower beam 66, while being a box beam, is still small enough to fit between the left and right legs 36 and 38 of the supporting units S when those legs swing between their upright and depressed positions (FIG. 2). Moreover, the lower beam 66 has bumpers 8ll fastened to the sides thereof, and these bumpers 81 align with the cross bars 40 and 42 of the supporting units S when the legs supporting those cross bars are in their upright supporting positions. The bumpers 81 push against the raised cross bars 40 and 42 and move the upright legs 36 and 38 to which they are attached to their depressed positions as the gantry press P moves by them. For example, as the gantry press moves to the right, the bumpers 81 on the lower beam 66 will engage the raised cross bar 40 of the next supporting unit S and push that bar along with the legs 36 downwardly to their depressed position. This in turn will cause the left legs 38 of the supporting unit S to move upwardly to their upright positions, and when they rise they will be on the other side of the beam 66.

The upper cross beam 68 is likewise a box beam and includes (FIGS. 2 and 4) a lower plate 82 which is somewhat wider than the remainder of the beam. Consequently, the lower plate 82 projects beyond the remainder of the beam 68 in the provision of flanges 84. These flanges 84 form a track for two hydraulic press units 86, and each press unit has a mounting plate 88 which extends beneath the lower plate 82 of the upper beam 68 and is fitted with end plates 90 at its ends. The end plates 90 in turn are provided with rollers 91 which ride on the flanges 84 formed by the top plate 82. The mounting plate 88 has the barrel 92 of a hydraulic cylinder fastened to it with the axis of the cylinder being vertical, and the piston rod 94 of the cylinder projects from the lower end of the barrel 92. The piston rod 94 in turn carries a reinforced press platen 96.

One of press units 86 is propelled along the upper beam 68 by a rotary-type hydraulic motor (FIG. 4) mounted on the beam 68 at one end thereof. The motor 100 drives a chain 102 which extends the length of the beam 68 and is trained around sprockets 104 at the ends of the beam 68. The chain 102 attaches to the end plate 90 of one of the press units. The other press unit 86 is also connected to another chain 102 located on the other side of the beam 68, and that chain is operated by a hand wheel 106 positioned at the end of the beam which is above the carriage 52. Actually, the hand wheel rotates a sprocket over which the other chain 102 is trained. The gantry press P may be provided with only one press unit 86.

The frame 50 of the gantry press P carries a hydraulic system which includes (FIG. 1) a pump and control valves 122 for directing the high pressure hydraulic fluid delivered by the pump 100 to the motors 58 of the carriages 52 and 54 and to the barrels 92 of the hydrau lic press units 86. The fluid reservoir for the hydraulic system is the interior of the upper cross beam 68. The control valves 122 are operated by handles 124 located at one end of the upper cross beam 68, and the carriage 52 at that end is provided with a platform 126 on which the operator stands to manipulate the handles 124.

The jigging pads J rest on the platform 10 and are secured thereto at the channels 16. Each pad J includes (H686 and 7) a raised plate 130 having horizontal flanges 132 at its sides and these flanges have longitudinal slots 134 through which bolts 136 extends. The bolts 136 project between the inwardly turned flanges 18 of the channels and thread into retaining elements 138 disposed within the channels 16. The retaining elements 138 are rectangular so they do not become cocked in the channels 16, and are furthermore wider than the spacing between the inwardly turned flanges 18 so they cannot be withdrawn upwardly from the channels 16. When the bolts 136 are tightened, the flanges 18 of the pad J are clamped firmly to the channel 16 into which the bolts 136 extend, and hence the pad J is fixed in position on the platform 10. However,

when the bolts 136 are loosened, the pad J may be moved both longitudinally and transversely of the platform 10.

The jigging pad J is also provided (FIG. 6) with abutment bars 140 against which workpieces abut, and may further be provided with eccentric clamps 142 for urging the workpieces against the abutment bars 140.

The jigging pad J located beneath the apex of the truss configuration has a locating bar 144 which is hinged to that pad about a hinge pin 14-6 extending in the direction of the channels 16. The pin 146 is located adjacent to the outer margin of the pad J and normally the bar 144 projects outwardly away from the pad. However, the bar 144 may be swung over the top surface of the plate 130, in which case one side thereof may be used as a center line for locating the pieces of lumber 152.

OPERATION The truss fabricating machine M is used to drive conventional connector plates 150 (FIGS. 6 and 7) into abutting pieces of lumber 152 to form trusses and other similar structures. The connector plates 150 are merely galvanized plates having sharp prongs struck from them at 90. The lumber 152 should be cut so that the sides or end faces of adjoining pieces facewise abut.

After the lumber for the truss or other structure is cut it is laid together on the platform 10 of the table T in the desired truss configuration. Thereafter, with the truss configuration in the proper position, the gripping pads J are placed beneath the areas of abutment for the various pieces of lumber 152 in the truss, and then the jigging pads J are fastened firmly to the platform table 10. In this regard, it will be recalled that the pads J may be moved both transversely and longitudinally by loosening the bolts 136. The transverse movement is however limited by the length of the slots 134, and should that movement be insufficient, the bolts 136 may be extended into and engaged with retaining elements 138 in different channels 16. As the pads J are positioned and secured to the platform 10, the abutment bars 140 are moved to and secured in the proper position on the raised plates 130 of those pads J.

Once the jigging pads J are properly located and the abutment bars 140 correctly positioned thereon, a connector plate 150 is laid on the raised plate 130 of each pad J with its sharp prongs projecting upwardly. Moreover, the plates 150 are located such that they will bridge the line of abutment between the two pieces of lumber which meet at that pad J. Next the lumber 152 is laid into the truss configuration using the abutment bars on the pads J to properly locate that lumber.

The eccentric clamps 142 are then closed to hold the lumber 152 in place. Thereafter, more connector plates 150 are placed over the lumber such that they also bridge the lines of abutment, but these plates have their sharp prongs projecting downwardly.

Initially, the gantry press P is at one end of the jigging table T, but once the connector plates 150 and lumber 152 are correctly positioned on the jigging pads J, the gantry press P is moved by directing hydraulic fluid to the motors 58 of the carriages 52 and 54. As the gantry press P moves the bumpers 81 on the leading side of its lower cross beam 66 strike the cross bar or 42, whichever is in the elevated position, and swing the legs 36 or 38 supporting that bar to their depressed positions (FIGS. 2). In particular, assuming that the gantry press P moves from left to right, its lower beam 66 passes over the horizontally disposed left legs 38 of the first supporting unit S encountered. The upright right legs 36 of that supporting unit S, however, lie in the path of the lower beam 66 and in time the bumpers 81 on the lower beam 66 engage the cross beam 40 on those upright legs 36. When this occurs, the upper ends of the upright legs 36 are pushed forwardly and the cross bar 40 attached to those ends slides forwardly beneath the table platform 10. Actually, the movement of the upright legs 36 is rotational inasmuch as they are connected to the pivot shaft 34 which rotates in the sleeves 32. Eventually, the right legs 36 on the leading side of the beam 66 come to the horizontal depressed position and the beam 66 passes over them. While the right legs 36 on the leading side of the beam 66 move to the depressed position, the left legs 38 on the trailing side of the beam 66 raise upwardly to the upright position, due to the fact that corresponding right and left legs 36 and 38 are joined to form a unitary structure. Thus, as the gantry press P passes over a supporting unit S the leading legs for that supporting unit S move into their depressedposition, and the trailing legs as sume the upright supporting position. During the transition from leading to trailing legs (FIG. 2), the portion of the platform 10 normally supported by those legs is supported on the rollers 74 along the upper edges of the lower beam 66. Since the'legs 36 and 38 at each side of the supporting units 5 are connected through the pivot shaft 34, they move in unison. Thus, no side thrusts are applied by the moving gantry press and the chances of the supporting unit S being wrenched from the floor F at their base plates 30 are minimal.

The gantry press P is advanced by its operator until the upper beam 68 is located directly over the first connector plate 150. Once this position is reached, further movement of the gantry press P is terminated and one of the press units 86 is moved along the upper beam 68 until its platen 96 is located directly over the first connector plate 150. A skilled operator can perform the two positioning operations simultaneously. Thereupon hydraulic fluid is directed to the cylinder barrel 92 to drive the piston rod 94 downwardly, and this in turn forces the platen 96 against the first connector plate 150. The platen 96 is driven downwardly until the pressure of the fluid within the barrel 92 reaches a prescribed value. The force applied to the lumber is resisted by the lower beam 66. More specifically, as the downwardly directed force is applied to the lumber 152 it is also transmitted to the table platform 10 through the jigging pad J. This portion of the platform 10, however, is supported on the rollers 74, but since the rollers 74 are spring loaded they depress, allowing the platform 10 to rest on the top plate 72 of the lower beam.

Thus, the top plate 72 serves as an anvil for resisting the force applied by the press units 86.

The force applied to the two connector plates 150 is large enough to drive the prongs of those connector plates 150 completely into the abutting pieces of lumber 152. Thus, when the platen 96 is withdrawn the connector plates 150 remain embedded in the pieces of lumber 152, spanning the line of abutment between those two pieces to hold them firmly together.

Thereafter, the gantry press P is advanced to the next jigging pad J and set of connector plates 150 thereon where the foregoing procedure is repeated. Should two sets of connector plates 150 be in transverse alignment on the table platform 10, then both press units 86 may be utilized to simultaneously drive those sets of plates 150 into the lumber 152. The procedure is repeated until all of the connector plates 150 are driven into the lumber 152. Then the eccentric clamps 142 are released and the completed truss or other structure is lifted from table platform 10.

Usually a building will contain many trusses of identical configuration. Hence, the jigging pads J are used without change in position until the required number of trusses are fabricated.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A machine for joining two pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line abutment between the two or more pieces; said machine comprising: a platform having a generally flat upper surface for supporting the lumber and parallel channels which open upwardly, the channels having inwardly turned flanges; retaining elements disposed in the channels and being wider than the spacing between the flanges of the channels; jigging pads disposed on the platform and having slots extending generally perpendicular to the channels, the jigging pads being fastened to the platform by connecting means which extend through the slots and engage the retaining elements in the channels; supporting units for supporting the platform in an elevated position, each supporting unit including at least two leading legs which are connected firmly together and move simultaneously from an upright supporting position wherein they support the platform to a depressed position wherein they do not support the platform, and trailing legs which are connected firmly together and are also connected with the leading legs to move to the upright position as the leading legs move to the depressed position; and a gantry press movable along the platform and including a lower beam which passes beneath the platform and moves the leading legs to their depressed positions as it does, an upper beam disposed above the platform, connecting beams interconnecting the upper and lower beams, and press means carried by the upper beam for forcing the prongs of the connector plate into the lumber.

2. A machine according to claim 1 wherein the plat form bears against the lower beam as the press means forces the connector plate into the lumber, whereby the lower beam serves as an anvil for resisting the force applied by the press means.

3. A machine according to claim 2 wherein the gantry press further includes spring loaded rollers, the circumferential surfaces of which project above the lower beam and support the platform as the gantry press moves, the rollers being shiftable in a downward direction against the spring loading so that they will be depressed when the press means forces the connector plate into the lumber, thus enabling the platform to bear against the lower beam.

4. A machine according to claim 1 wherein the gantry press further comprises a carriage at each end thereof having wheels which ride along tracks, one of the carriages being mounted rigidly with respect to the upper and lower beams and the other carriage being free to pivot relative to the beams so that the wheels of the carriages will remain engaged with the tracks notwithstanding irregularities in the tracks.

5. A machine for joining two or more pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line of abutment between the two pieces, said machine comprising: a platform having a generally flat upper surface and including upwardly opening channels provided with inwardly turned flanges; retaining elements in the channels and being wider than the spacing between the inwardly turned flanges so that the elements will slide along the channels but cannot be withdrawn upwardly therefrom; jigging pads on the platform for supporting the lumber, the jigging pads having slots which extend generally perpendicular to the channels; bolts extended through the slots in the jigging pads and threaded into the retaining elements in the channels for firmly securing the pads to the platform; support units beneath the platform for supporting the platform intermediate its ends, each support unit including at least one leading leg which moves from an upright position wherein it supports the platform to a depressed position wherein it does not support the platform and a trailing leg which is connected to the leading leg and also moves between an upright supporting position and a depressed non-supporting portion, the trailing leg being in its depressed position when the leading leg is in its upright position, and vice-versa; and a gantry press movable along the platform and including a lower beam which passes beneath a platform and moves the leading legs of the supporting units to their depressed positions as it does, an upper beam disposed above the platform, connecting beams interconnecting the upper and lower beams, and press means carried by the upper beam for forcing the prongs of the connector plate into the lumber.

6. A machine according to claim 5 wherein the pads are provided with adjustable abutment bars against which the lumber abuts and is thereby positioned on the platform.

7. A gantry press to press pronged connector plates into lumber resting on a platform supported on legs which depress to permit passage of the press along the platform; said press comprising: carriages having wheels, a lower beam supported on the carriages and extended beneath the platform, an upper beam extending over the platform, the upper beam having flanges extending laterally from it; connecting beams extended upwardly above the lower beam for supporting the upper beam relative to the lower beam; a press assembly mounted on and movable along the upper beam and including a mounting plate extended beneath the upper beam and provided with end members having rollers which ride on the flanges, a hydraulic cylinder barrel mounted on the plate with its axis extended downwardly toward the lower beam, a piston rod in the barrel, and a platen on the lower end of the piston rod for engaging the connector plates and forcing the prongs of the connector plates into the lumber.

8. A gantry press according to claim 7 wherein the press assembly is one of two press assemblies mounted on the upper beam.

9. A gantry press according to claim 7 wherein the gantry press includes a pump carried thereby for raising the pressure of hydraulic fluid, and a control valve for directing the high pressure hydraulic fluid to the hydraulic cylinder; and wherein the upper beam is a box beam, the interior of which serves as a reservoir for hydraulic fluid.

10. A gantry press according to claim 7 wherein the lower beam carries spring loaded rollers which normally project slightly above the upper surface of the lower beam and support the platform as the. press moves along it, the rollers being depressable in the downward direction against the spring load, whereby the press assembly acts against the lumber and forces the platform and rollers downwardly until the platform bears against the lower beam so that the lower beam resists the force applied by the press assembly.

11. A gantry press according to claim 7 wherein one carriage is fastened rigidly to the lower beam and the other carriage is provided with a bridge bearing on which the lower beam rests, the axis of the bridge bearing being transverse to the direction of movement, whereby the wheels of the carriages will remain against irregular track surfaces.

12. A machine for joining two pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line of abutment between the two pieces, said machine comprising: a platform having a generally flat upper surface for supporting the lumber; a plurality of supporting units beneath the'platform for supporting the platform in an elevated position, each supporting unit having at least two spaced apart leading legs located at opposite sides of the platform at least two spaced apart trailing legs also located at opposite sides of the platform, and connecting members extending transversely of the platform and joining the legs together into a generally rigid unit, each supporting unit being capable of pivoting between two supporting positions about an axis spaced downwardly from the platform and extended transversely with respect thereto, each supporting unit when in the first supporting position being engaged with the underside of the platform at the ends of the leading legs and supporting the platform through the leading legs, each supporting unit when in the second supporting position being engaged with the underside of the platform at the ends of the trailing legs and supporting the platform through the trailing legs, the trailing legs being spaced downwardly from the underside of the platform when the platform is supported by the leading legs and the leading legs being spaced downwardly from the underside of the platform when the platform is supported by the trailing legs; parallel tracks extended longitudinally of the platform outwardly from the supporting units; and a gantry press having wheels on the tracks and a motor connected to at least one of the wheels for driving that wheel so as to move the gantry press along the tracks, the gantry press being adapted to move the supporting units from one supporting position to the other supporting position as it moves past them along the tracks, whereby the legswhich support the platform are changed, the gantry press further having a lower beam which extends beneath the platform, an upper beam which extends over the platform, connecting beams interconnecting the upper and lower beams at the sides of the platform, and press means carried by the upper beam for forcing the prongs of the connectors into the lumber, the lower beam supporting the platform as the press means forces the connectors into the lumber and being configured to fit between the leading and trailing legs of each supporting unit as that supporting unit changes positions.

13. A machine according to claim 12 wherein each support unit includes a pivot shaft to which the leading and trailing legs are firmly attached, and wherein fixed bearings are provided in which the pivot shaft rotates.

14. A machine according to claim 13 wherein the connecting members include a cross bar extended across the ends of the leading legs, and another cross bar extended across the ends of the trailing legs.

15. A machine according to claim 14 wherein the cross bars are located over center relative to the axis of the pivot shaft when the legs to which they are attached are in their upright supporting positions. 

1. A machine for joining two pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line abutment between the two or more pieces; said machine comprising: a platform having a generally flat upper surface for supporting the lumber and parallel channels which open upwardly, the channels having inwardly turned flanges; retaining elements disposed in the channels and being wider than the spacing between the flanges of the channels; jigging pads disposed on the platform and having slots extending generally perpendicular to the channels, the jigging pads being fastened to the platform by connecting means which extend through the slots and engage the retaining elements in the channels; supporting units for supporting the platform in an elevated position, each supporting unit including at least two leading legs which are connected firmly together and move simultaneously from an upright supporting position wherein they support the platform to a depressed position wherein they do not support the platform, and trailing legs which are connected firmly together and are also connected with the leading legs to move to the upright position as the leading legs move to the depressed position; and a gantry press movable along the platform and including a lower beam which passes beneath the platform and moves the leading legs to their depressed positions as it does, an upper beam disposed above the platform, connecting beams interconnecting the upper and lower beams, and press means carried by the upper beam for forcing the prongs of the connector plate into the lumber.
 2. A machine according to claim 1 wherein the platform bears against the lower beam as the press means forces the connector plate into the lumber, whereby the lower beam serves as an anvil for resisting the force applied by the press means.
 3. A machine according to claim 2 wherein the gantry press further includes spring loaded rollers, the circumferential surfaces of which project above the lower beam and support the platform as the gantry press moves, the rollers being shiftable in a downward direction against the spring loading so that they will be depressed when the press means forces the connector plate into the lumber, thus enabling the platform to bear against the lower beam.
 4. A machine according to claim 1 wherein the gantry press further comprises a carriage at each end thereof having wheels which ride along tracks, one of the carriages being mounted rigidly with respect to the upper and lower beams and the other carriage being free to pivot relative to the beams so that the wheels of the carriages will remain engaged with the tracks notwithstanding irregularities in the tracks.
 5. A machine for joining two or more pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line of abutment between the two pieces, said machine comprising: a platform having a generally flat upper surface and including upwardly opening channels provided with inwardly turned flanges; retaining elements in the channels and being wider than the spacing between the inwardly turned flanges so that the elements will slide along the channels but cannot be withdrawn upwardly therefrom; jigging pads on the platform for supporting the lumber, the jigging pads having slots which extend generally perpendicular to the channels; bolts extended through the slots in the jiggIng pads and threaded into the retaining elements in the channels for firmly securing the pads to the platform; support units beneath the platform for supporting the platform intermediate its ends, each support unit including at least one leading leg which moves from an upright position wherein it supports the platform to a depressed position wherein it does not support the platform and a trailing leg which is connected to the leading leg and also moves between an upright supporting position and a depressed non-supporting portion, the trailing leg being in its depressed position when the leading leg is in its upright position, and vice-versa; and a gantry press movable along the platform and including a lower beam which passes beneath a platform and moves the leading legs of the supporting units to their depressed positions as it does, an upper beam disposed above the platform, connecting beams interconnecting the upper and lower beams, and press means carried by the upper beam for forcing the prongs of the connector plate into the lumber.
 6. A machine according to claim 5 wherein the pads are provided with adjustable abutment bars against which the lumber abuts and is thereby positioned on the platform.
 7. A gantry press to press pronged connector plates into lumber resting on a platform supported on legs which depress to permit passage of the press along the platform; said press comprising: carriages having wheels, a lower beam supported on the carriages and extended beneath the platform, an upper beam extending over the platform, the upper beam having flanges extending laterally from it; connecting beams extended upwardly above the lower beam for supporting the upper beam relative to the lower beam; a press assembly mounted on and movable along the upper beam and including a mounting plate extended beneath the upper beam and provided with end members having rollers which ride on the flanges, a hydraulic cylinder barrel mounted on the plate with its axis extended downwardly toward the lower beam, a piston rod in the barrel, and a platen on the lower end of the piston rod for engaging the connector plates and forcing the prongs of the connector plates into the lumber.
 8. A gantry press according to claim 7 wherein the press assembly is one of two press assemblies mounted on the upper beam.
 9. A gantry press according to claim 7 wherein the gantry press includes a pump carried thereby for raising the pressure of hydraulic fluid, and a control valve for directing the high pressure hydraulic fluid to the hydraulic cylinder; and wherein the upper beam is a box beam, the interior of which serves as a reservoir for hydraulic fluid.
 10. A gantry press according to claim 7 wherein the lower beam carries spring loaded rollers which normally project slightly above the upper surface of the lower beam and support the platform as the press moves along it, the rollers being depressable in the downward direction against the spring load, whereby the press assembly acts against the lumber and forces the platform and rollers downwardly until the platform bears against the lower beam so that the lower beam resists the force applied by the press assembly.
 11. A gantry press according to claim 7 wherein one carriage is fastened rigidly to the lower beam and the other carriage is provided with a bridge bearing on which the lower beam rests, the axis of the bridge bearing being transverse to the direction of movement, whereby the wheels of the carriages will remain against irregular track surfaces.
 12. A machine for joining two pieces of abutting lumber with a connector plate having prongs projecting therefrom and positioned such that it bridges the line of abutment between the two pieces, said machine comprising: a platform having a generally flat upper surface for supporting the lumber; a plurality of supporting units beneath the platform for supporting the platform in an elevated position, each supporting unit having at least two spaced apart leading legs located at opposite sideS of the platform at least two spaced apart trailing legs also located at opposite sides of the platform, and connecting members extending transversely of the platform and joining the legs together into a generally rigid unit, each supporting unit being capable of pivoting between two supporting positions about an axis spaced downwardly from the platform and extended transversely with respect thereto, each supporting unit when in the first supporting position being engaged with the underside of the platform at the ends of the leading legs and supporting the platform through the leading legs, each supporting unit when in the second supporting position being engaged with the underside of the platform at the ends of the trailing legs and supporting the platform through the trailing legs, the trailing legs being spaced downwardly from the underside of the platform when the platform is supported by the leading legs and the leading legs being spaced downwardly from the underside of the platform when the platform is supported by the trailing legs; parallel tracks extended longitudinally of the platform outwardly from the supporting units; and a gantry press having wheels on the tracks and a motor connected to at least one of the wheels for driving that wheel so as to move the gantry press along the tracks, the gantry press being adapted to move the supporting units from one supporting position to the other supporting position as it moves past them along the tracks, whereby the legs which support the platform are changed, the gantry press further having a lower beam which extends beneath the platform, an upper beam which extends over the platform, connecting beams interconnecting the upper and lower beams at the sides of the platform, and press means carried by the upper beam for forcing the prongs of the connectors into the lumber, the lower beam supporting the platform as the press means forces the connectors into the lumber and being configured to fit between the leading and trailing legs of each supporting unit as that supporting unit changes positions.
 13. A machine according to claim 12 wherein each support unit includes a pivot shaft to which the leading and trailing legs are firmly attached, and wherein fixed bearings are provided in which the pivot shaft rotates.
 14. A machine according to claim 13 wherein the connecting members include a cross bar extended across the ends of the leading legs, and another cross bar extended across the ends of the trailing legs.
 15. A machine according to claim 14 wherein the cross bars are located over center relative to the axis of the pivot shaft when the legs to which they are attached are in their upright supporting positions. 